Spinal fixation devices are used in orthopedic surgery to align and/or fix a desired relationship between adjacent vertebral bodies. Such devices typically include a spinal connector, such as a spinal rod, that is coupled to adjacent vertebrae by attaching the element to various anchoring devices, such as hooks, bolts, wires, or screws. The spinal rods can have a predetermined contour that has been designed according to the properties of the target implantation site, and once installed, the spinal rod and the anchors holds the vertebrae in a desired spatial relationship, either until desired healing or spinal fusion has taken place, or for some longer period of time.
Spinal connectors, such as spinal rods, can be anchored to specific portions of the vertebra. Since each vertebra varies in shape and size, a variety of anchoring devices have been developed to facilitate engagement of a particular portion of the bone. Pedicle screw assemblies, for example, have a shape and size that is configured to engage pedicle bone. Such screws typically include a threaded shank that is adapted to be threaded into a vertebra, and a head portion having a rod-receiving element, usually in the form of a U-shaped slot formed in the head. A set-screw, plug, or similar type of fastening mechanism, is used to lock the spinal rod into the rod-receiving head of the pedicle screw. In use, the shank portion of each screw is threaded into a vertebra, and once properly positioned, a spinal rod is seated through the rod-receiving member of each screw and the rod is locked in place by tightening a set screw or other fastener mechanism to securely interconnect each screw and the spinal rod.
While current spinal fixation systems have proven effective, one challenge associated with such systems is mounting the spinal rods into the rod-receiving member of various fixation devices. In particular, it can be difficult to align and seat the rod into the rod receiving portion of adjacent anchors due to the positioning of the vertebra into which the anchors are mounted. Thus, the use of a spinal rod reduction device, also sometimes referred to as a spinal rod approximator, is often required in order to grasp the head of the anchor and reduce the rod into the rod-receiving head of the bone anchor.
While several rod reduction devices are known in the art, some tend to be bulky and cumbersome to use and, thus, are unsuitable for use all procedures, particularly in minimally invasive surgical procedures in which the skin incisions and tissue pathways to the spine are relatively small and restricted. Accordingly, there is a need for improved rod reduction devices and methods for seating a spinal rod in a rod-receiving member of one or more spinal anchors.